Hello I am trying to get rows using Groovy Sql connection but it returns me records as a List inside a List. The following:
Sql sql = new Sql(dataSource)
List<GroovyRowResult> row = sql.rows('select * from user where username=:userName and password=:password, [userName:'groovy',password:'123'])
returns the result as [[return record as map]]
Any one help me to figure out why the result is a List inside a List. How will I get it as a single level List using the rows method?
Your results are coming back as a list of maps, not a list of lists. Look at the ':' and ',' chars in the inner part. You can use standard groovy extraction of values from these.
In your case, it looks like you're using a primary key search, so will only return one result, so use firstRow in this case, so that you don't have to extract the single map result from the list.
See the documentation for the groovy Sql class for examples.
In the more general case where you are returning multiple rows, then your data probably looks like this:
[[username:"foo", password:"foopass"], [username:"bar", password:"barpass"]]
Assuming the line:
def results = sql.rows('select * from user')
You can then do things like spread operators:
assert results.username == ["foo", "bar"]
assert results.password == ["foopass", "barpass"]
or iterate over the results
results.each { println it.username }
==> foo
==> bar
or use any of the many Collection functions
println results.collect { "${it.username} -> ${it.password}" }
==> [ "foo -> foopass", "bar -> barpass" ]
I think your main issue was not recognising a single map entry in a list.
It doesn't return a List inside a List, it returns a List of Map with each map containing the columns selected from your select.
So if you want all of the usernames selected (as a List), you can just do:
def usernames = row.username
If you just want a single row, you can do:
GroovyRowResult row = sql.firstRow('select * from user where username=:userName and password=:password, [userName:'groovy',password:'123'])
And then this will effectively just be a map with each key being the field name selected, and each value being the value of the first row of each field
Related
I use ruby-2.3 and oci-8 gem. I want to make the select query:
stm = "select * from DATASERVICEUSERS t where boss<>100 and loginad is not null"
res = CONN.exec(stm).fetch_hash do |row|
#do something with row
end
CONN.logoff
How can I query the result of the whole to put for example in an array or hash, instead of cycle pass through each record? I need just a collection of elements of the result of this request.
Oci-8 doesn't provice that. The .exec method produces a cursor that you you need to process like your code demonstrates. You can fill up an array with an array of fields or a hash.
Here an example for an array
records = []
conn.exec(sql) { |record| records << record}
# records: [["xxxx", "xxxx"], ["yyyy", "yyyy"], ..]
I know this is quite an old question but I've come across this problem. I'm not as well versed in ruby but oci8 2.2.7 actually provides fetch_hash
https://www.rubydoc.info/gems/ruby-oci8/OCI8/Cursor#fetch_hash-instance_method
here's an example from my use case:
records = []
dataCursor = #odb.exec(queryUUNRData)
while((data = dataCursor.fetch_hash) != nil)
records.push data
end
dataCursor.close
the resulting dataset already includes the column names as hash key
How can i compare array of elements with the linq query. I will pass array of elements to the controller and i want to compare and display the records that only contains the passed elements.
I will pass an array of values like ["first","second","third"] and i want to compare these records with the linq query and generate the result that contains these three records
I'm not sure but you probably want something like this
String[] values = {"first", "second", "third"};
List<YourObject> query =
(from p in this.db.table
where values.Contains(p.values) select p).ToList();
I have a legacy database that has data elements stored as a comma delimited list in a single database field. (I didn't design that, I'm just stuck with it.)
I have a list of strings that I would like to match to any of the individual values in the "array" in the DB field and am not sure how to do this in Linq.
My list:
List<string> items= new List<string>();
items.Add("Item1");
items.Add("Item2");
The DB field "Products" would contain data something like:
"Item1,Item3,Item4"
"Item3,Item5,Item6"
"Item2,Item7,Item6"
"Item1,Item2"
"Item1"
My first pass at the Linq query was:
var results = (from o in Order
.Where(p=> items.Contains(p.Products)
But I know that won't work. because it will only return the records that contain only "Item1" or "Item2". So with the example data above it would return 0 records. I need to have it return two records.
Any suggestions?
There is a simple clever trick for searching comma-separated lists. First, add an extra , to the beginning and end of the target value (the product list), and the search value. Then search for that exact string. So for example, you would search ,Item1,Item3,Item4, for ,Item1,. The purpose of this is to prevent false positives, i.e., Item12,Item3 finding a match for Item1, while allowing items at the beginning/end of the list to be properly found.
Then, you can use the LINQ .Any method to check that any item in your list is a match to the product list, like the following:
var results = (from o in Order
.Where(o => items.Any(i => (","+o.Products+",").Contains(","+i+",")))
One way would be to parse the list in the Products field:
var results = (from o in Order
.Where(o => items.Any(i => o.Products.Split(',').Contains(i))
But that would parse the string multiple times for each record. You could try pulling back ALL of the records, parsing each record once, then doing the comparison:
var results = from o in Order
let prods = o.Products.Split(',')
where items.Any(i => prods.Contains(i))
select o;
I have a data table containing multiple columns and one column that stores somewhat complex text patterns - I need to parse the field to determine if a particular sub strings exist in specific positions within the larger string pattern and then if the record should be filtered out as a result.
I can't see a way to perform the parse other than by writing a C# parsing function with String.Split method calls, foreach, etc. But if I try to parse like this:
var myFilteredTable = _db.MyTable.Where(t => t.Column1 == 'Filter1'
&& ParseIsMyItemInColumn2(t) );
I get "has no supported translation to SQL" errors.
The other option I thought of was to build the initial result without the Parse:
var myFilteredTable = _db.MyTable.Where(t => t.Column1 == 'Filter1' );
and iterate through the IQueryable resultset, testing each row with the parse function, to filter out the unwanted rows, but IQueryable does not have Remove function to strip out unwanted rows nor Add function to allow me to build up a new resultset.
So how can I filter in linq when I also need to write a Parse function?
Well the "initial filter in the database then do the rest locally" is easy:
var filtered = _db.MyTable.Where(t => t.Column1 == "Filter1")
.AsEnumerable() // Do the rest locally
.Where(t => ParseIsMyItemInColumn2(t));
AsEnumerable is a simple pass through method, but because the result is typed as IEnumerable<T> rather than IQueryable<T>, the subsequent LINQ operations use the LINQ to Objects methods in Enumerable rather than the ones in Queryable.
Obviously if a lot of items match the first filter but fail the second, that won't be terribly efficient...
Unfortunately, if the "parse function" is not something that can be translated to SQL, you will need to pull the results and use LINQ to Objects:
var myFilteredTable = _db.MyTable.Where(t => t.Column1 == 'Filter1')
.AsEnumerable().Where(ParseIsMyItemInColumn2);
Note that this will stream all of the results into memory, and then perform your parse.
I'm using NHibernate 3.2 and I have a repository method that looks like:
public IEnumerable<MyModel> GetActiveMyModel()
{
return from m in Session.Query<MyModel>()
where m.Active == true
select m;
}
Which works as expected. However, sometimes when I use this method I want to filter it further:
var models = MyRepository.GetActiveMyModel();
var filtered = from m in models
where m.ID < 100
select new { m.Name };
Which produces the same SQL as the first one and the second filter and select must be done after the fact. I thought the whole point in LINQ is that it formed an expression tree that was unravelled when it's needed and therefore the correct SQL for the job could be created, saving my database requests.
If not, it means all of my repository methods have to return exactly what is needed and I can't make use of LINQ further down the chain without taking a penalty.
Have I got this wrong?
Updated
In response to the comment below: I omitted the line where I iterate over the results, which causes the initial SQL to be run (WHERE Active = 1) and the second filter (ID < 100) is obviously done in .NET.
Also, If I replace the second chunk of code with
var models = MyRepository.GetActiveMyModel();
var filtered = from m in models
where m.Items.Count > 0
select new { m.Name };
It generates the initial SQL to retrieve the active records and then runs a separate SQL statement for each record to find out how many Items it has, rather than writing something like I'd expect:
SELECT Name
FROM MyModel m
WHERE Active = 1
AND (SELECT COUNT(*) FROM Items WHERE MyModelID = m.ID) > 0
You are returning IEnumerable<MyModel> from the method, which will cause in-memory evaluation from that point on, even if the underlying sequence is IQueryable<MyModel>.
If you want to allow code after GetActiveMyModel to add to the SQL query, return IQueryable<MyModel> instead.
You're running IEnumerable's extension method "Where" instead of IQueryable's. It will still evaluate lazily and give the same output, however it evaluates the IQueryable on entry and you're filtering the collection in memory instead of against the database.
When you later add an extra condition on another table (the count), it has to lazily fetch each and every one of the Items collections from the database since it has already evaluated the IQueryable before it knew about the condition.
(Yes, I would also like to be the extensive extension methods on IEnumerable to instead be virtual members, but, alas, they're not)